Enlite sensor tips I got from Medtronics

Hi everyone,
I thought I'd pass along some tips a Medtronic trainer gave me the other day.

Some background, I've had issues with sensors on and off since I started my 530g(got it in May). Basically two main issues, poor performance in the first 24 hours, and sensors not surviving the full 6 days. I've been a good trooper and called the Medtronic helpline each time I had problems so they could document them, and so I could get a replacement sensor(at no charge). I then had the helpline contact my regional clinical manager to see if they could see if I was doing something wrong or if they had suggestions. I then met with my local Medtronics clinical manager who is a RN, CDE, AND a Type 1 that uses the 530g. This was only a week ago so I'll just give you the tips that I know help.

Poor performance in the first 24 hours was driving me insane.
Tip 1: The first calibration needs to be done when your "Cal Factor" is between 3-8. Cal Factor = "Current fingerstick BG divided by the current "Sensor Isig" value. Sensor Isig can be found on the Sensor Status screen. If the "Cal Factor" is higher or lower, you will get bad readings for the next entire day since the the CGM uses the last 4 calibrations as a baseline. This has proven accurate

I use IV3000 as overtape for my Sensor mainly for comfort since I'm pretty physically active.
Tip 2: Each sensor comes with 2 pieces of overtape. Use one normally then cut another in half. Attach the sensor as you were taught to, plug in and secure the transmitter as normal. Then take half of the tape you cut and put it over the front of the sensor to make it more secure. You can then use the second half over the back third of the transmitter or do like me and cut an IV3000 in half and just put it over the back third of the Transmitter. This will keep the middle of the transmitter exposed so that water can drain easily when you shower while still giving you the security of overtaping.

I have been only attaching my sensor to my abdomen, mainly because I'm lean/muscular and didn't think I could attach it elsewhere.
Tip 3: We found a couple of alternative sites on me that might work for you. The inner thigh, I currently have my sensor here, its working like a charm and I can hardly tell it's there. The top of the butt below the beltline but above the part you sit on. I haven't tried this yet but it seems like it would work well.

That's all I have for now, I'll let you know if anything else comes along that might help.

Thanks, Kevin. My Enlite sensor training with the Medtronic rep is tomorrow. Great timing. The cal factor is new to me, but I used to look for a stable sensor isig reading before I calibrated with the old sensor.

Glad you found it helpful. The "Cal factor" won't be covered in regular CGM training for you, its only something they share 1v1 if needed after reviewing a couple months of Carelink data.
This is my first pump and my first CGM, I posted this because I could have used this information when I first got the 530g.

I've had it since May myself. Best info I've gotten was from my Nurse/CDE because he was a Type 1 with a pump himself--but not a Medtronic. I wish they would give us ALL that information from the beginning. I think most Type 1s are control freaks (because WE control our treatment) by necessity.

I have been using the Medtronic CGMS since the very first one became available. I always use my thighs because they do much better there. HOWEVER - the only place that is approved is the abdomen. If you call the helpline and tell them you used your thigh, they might not send you a replacement because you are using the sensor 'off label'. I just called today because I had one that refused to be accurate and on the 3rd day I got two cal errors and then a change sensor message. The person on the helpline did replace it, but made it clear that she did not have to do so. She said she was doing it as a 'courtesy'.

I found that using skin-tac prior to inserting the sensor really helps. I had issues with failed sensors and this really helped.

Do you leave a spot on your skin clear for the needle or do you insert through skin that has skin tac on it?

The trainer actually puts down Tegaderm on hers first then inserts, since she has very sensitive skin.
As for Medtronics, they will only replace a sensor if it was placed directly on the skin(no tape or barrier wipe) and if it was placed in the abdomen. This is because the FDA is actively reading their Helpline logs to make sure the 530g is safe.

I put the needle through the skin tac area. I have not had any issues.

thank you for Tip 1
i suspected, but never got a confirmation from them

The best info I’ve received from calling Medtronic is that sensor accuracy and cal errors depend on me making sure that my bg is stable and within my range without trending up or down: The sensor (caboose) can’t keep up with the meter (train engine) values. So I don’t eat before or after a sensor calibration. After the first 24 hrs,it is more forgiving. Excellent point about the bg & isig calculations/ratio, too.

For those of you who use Medtronic's CareLink to upload and ponder their pump's data, the "Calibration Factor" is one of the values provided in the Data Table report.

The "Calibration Factor" is included as part of the "Pump and sensor diagnostic info" check box for the Data Table report. But I think you would also want to check at least the "Sensor data" box as well.

I actually just check all the boxes to dump everything since I am never sure what might be of interest to me as I'm walking through a report.

Note: The "Calibration Factor" reported in the Data Table never appeared to be an exact match to the simple BG / ISIG calculation. It was close, but not identical. Possibly the value in the Data Table report is the result of the weighted average of the last four calibrations?

My calibration factor seemed to almost never be under 8. I'll have to try being more picky about my calibrations & see if it makes a difference in the accuracy of my SGs going forward.


I started using the Enlite sensors in November. The first 2 weeks were pretty awesome, and then it seems that after that, I've had nothing but issues. Every time I turn around it seems that I have a CAL ERROR. Or it senses my blood sugar is low and throws it into Threshold Suspend. I've talked to my trainer, they ran a report and they think that the sensor is going in ok, but is coming out and then going back in. So she sent me some Skin Tac stuff. I plan to try it this evening, however, she (she being my trainer) said to insert the sensor first, and then saturate the area with the Skin Tac. Has anyone tried this specifically? Her reasoning is that the sensor acts like a "screen" and if the skin tac gets on it during insertion, it won't work. Does anyone else have any other ideas?

BuckeyegirlOH wrote:
I've talked to my trainer, they ran a report and they think that the sensor is going in ok, but is coming out and then going back in.

When I had problems and called the Medtronic support #, the service rep used the term "pistoning" to refer to this behavior. I liked that. It seemed apt, evocative of the problem behavior it refers to.

I believe this could be a problem for both the Enlite & the older Harpoon, uh, Sof-sensor, sensors. Perhaps it was not as obvious (?) with the Harpoons because their longer sensor probe might have been less easily disturbed this way?

I also started CGM at the end of November. I have been using the Harpoons most of the time. Why? Because that's what I was prescribed ... though I was also given 4 Enlites by my CDE. The catch is that these Enlites "expired" back on Nov 16, so I can't expect much from the help line if I call support. Still, they are probably still working fine and thus worth trying/using, no?

How "tightly" did you overtape your sensor before your trainer suggested the "Skin Tac stuff"?

For me, taping is perhaps the second biggest learning curve with the Medtronic CGM sensors. After my experience with a possibly pistoning Enlite, I have decided to try to be a tad more "assertive" when I overtape all my sensors.

My plan is to see if stretching the overtape a bit when I apply it will help. My intent is to have the tape apply more tension to the sensor, holding it more firmly against my skin so it is less likely to "move around".

I got the idea from what is suggested/done in this "How to use an enlite sensor" youtube vid when the presenter describes how to apply the overtape, especially the bit starting around 3m 54s where she mentions giving the tape "a little stretch".

It is mostly just a theory for me at this point. I did apply a second layer of "stretched" overtap to my current sensor and I think that helped. But these things take time to prove out, no?

-irrational john
T1 LADA since ~1980, first pump: Minimed 507, currently Minimed 723 + CGM

Pretty much what I've experienced. I can go days with stable sensor readings then all hell breaks loose with sensor yo-yo, suspend, call error, change sensor, etc. Helpline always willing to send a new one, but that's no consolation for being awakened in the middle of the night with suspend alarm waking me and and wife. I have serious issues with being able to sleep as it is. I have an Endo appointment in a couple weeks and I'm going to seek a different solution. Love the convenience of the pump, but had enough of the sensor.

zander wrote: Love the convenience of the pump, but had enough of the sensor.

Depending on what resources are available to you, you might consider giving the Dexcom CGM a try rather than just giving up on CGM completely. The Dexcom users can't seem to praise it enough. I'm limited to Medtronic both because that's what I'm given and also by my nature. (I like to fiddle with stuff. ;-) )

-irrational john
T1 LADA since ~1980, first pump: Minimed 507, currently Minimed 723 + CGM

My trainer told me to go as tight as possible. This was before she sent Skin Tac. She reinterated it when I stared using skin tac. This is the first week using the skin tac and so far so good. I've not had any errors, and honestly didn't get a weak sensor signal until yesterday, which was day 4 of the sensor. So hopefully, this will actually fix at least this problem and I come up with no other issues :) Thank you so much for taking the time to respond. I really appreciate it :)

I've not had any errors, and honestly didn't get a weak sensor signal until yesterday, which was day 4 of the sensor.

I don't really consider the Weak Signal Alert an error. It's a basic design flaw.

It is just too easy to block communication between the transmitter & the pump. No doubt it's because of the apparently really low signal strength of the MiniLink transmitter. I expect Medtronic will try to improve this in the "Guardian™ 2 Link transmitter" used by the Minimed 640G, but that's only a speculation.

One plus is that the current MiniLink transmitter buffers the last 8 SGs (40 minutes). So if you move the pump next to the sensor when you get this alert, you shouldn't loose any data points if they reconnect "soon enough".

However, it's annoying to have to not only try to figure out where to insert the sensor but also try to think ahead about where you are going to wear the pump so that it will be "close enough" to the sensor site to have a meaningful conversation. <sigh/>

-irrational john
T1 LADA since ~1980, first pump: Minimed 507, currently Minimed 723 + CGM

I don't want to give up on CGM. It just doesn't seem like Enlite is going to do it. I mean how long do you have to stay with try this or try that or now try this. Stand on your head and whistle Dixie. It started out with I must be taping wrong and then onto orientation of the sensor/transmitter then where on my body and weak signal means I have to place them closer together than the 6-8 inches I'm currently doing. Seems to me Medtronics is more sales focused than patient focused. On a separate note, it also ticks me off that they are doing that inversion thing, if it hasn't already happened it will soon, so they don't have to pay US taxes.

zander wrote:
I don't want to give up on CGM. It just doesn't seem like Enlite is going to do it. I mean how long do you have to stay with try this or try that or now try this.

Well, if you can go with Dexcom without being penalized financially, I would suggest you think about it. However, rather than just switching and hoping for the best, I suggest you first talk with one of the Dexcom reps.

I can think of two reasons to chat with a rep. First, you'd of course just want to get more information about the system. But also, if you think you are interested in going with Dexcom, then try to arrange for a one week or longer trial of the Dexcom CGM before committing.

I've read that others have done this. The point being that given your bad experience with Medtronic's CGM you wouldn't want to commit to paying yet again only to find out the Dexcom system doesn't won't work for your either. Dexcom is fairly confident about their customer satisfaction so I think they would work with you on this.

My situation is different. I get my health care from a bureaucracy. My doctors pick which pump & CGM I use, but I don't have to pay out of pocket for it. So I'm limited to using Medtronic's equipment. But I've also been happy enough with the Medtronic system. I don't mind tweaking around with stuff so long as it works for me eventually. And this week it has ... pretty much. ;-)

-irrational john
T1 LADA since ~1980, first pump: Minimed 507, currently Minimed 723 + CGM